1. Field of the Invention
Methods and apparatuses consistent with the exemplary embodiments relate to an apparatus and system for converting wave energy based on oscillating water column type, and more particularly to an oscillating water column type apparatus for converting wave energy that may be installed in a simple structure under water by satisfying resonance conditions depending on only a hydraulic spring constant and added mass by movement of water, and a system thereof.
2. Description of the Prior Art
Of ocean energies, wave energy refers to the oscillating energy of seawater caused by wind. Waves refer to the reciprocating movement of seawater moving up and down or left and right, which are different from tidal currents. Wave power generation refers to getting electric energy from wave energy, and is currently in the spotlight as a future environmentally friendly energy source. More specifically, periodical up and down movements caused by waves or front and back movements of water particles are converted into mechanical kinetic energy, and then converted into electric energy.
The aforementioned energy converting apparatuses may be broadly classified into two types: movable body type energy converting apparatuses and oscillating water column type energy converting apparatuses. The former type apparatuses obtain energy by movement of the floating body itself such as up-and-down movement or rotational movement of the floating body, whereas the latter type apparatuses obtain energy by air flow caused by the up-and-down movement of the water column inside the air chamber according to waves.
The energy converting apparatus according to the present invention belongs to the latter type, that is the oscillating water column type energy converting apparatuses, but it operates in another unique method, unlike conventional oscillating water column type energy apparatuses. Conventional oscillating water column type energy apparatuses are broadly classified into fixed type apparatuses such as U.S. Pat. No. 4,441,316 A and WO 2008/149084, and floating type apparatuses such as U.S. Pat. No. 4,858,434 A, whereas the energy converting apparatus of the present invention has a big difference since it is a submersible oscillating water column type energy converting apparatus that is based on changes in water pressure of the lower part of the housing that is relatively near the water surface.
Such an oscillating water column type energy converting apparatus generally has a shape of a buoy, and the resonance frequency corresponding to the movement of waves is determined according to its shape and mass. The buoy also makes vibratory movement according to the movement of waves, and the energy is converted into electric energy through a generator.
However, conventional oscillating water column type energy converting apparatuses are installed on the surface of water, and may thus be easily damaged or swept away in cases of by marine disasters such as storms and tidal waves etc. Furthermore, conventional energy converting apparatuses such as those disclosed in International Patent Publication WO 2008/149084 (published on Dec. 11, 2008) need a pressure adjustment apparatus and an additional spring in order to match the peak period of the waves of the sea where the apparatus is installed to the unique period of the apparatus. Herein, since additional mechanical components such as a bushing and an LM (Linear Motion) for restricting the movement of the apparatus are needed, the structure becomes complicated. Furthermore, conventional energy converting apparatuses such as those disclosed in International Patent Publication in WO 2008/149084 (published on Dec. 11, 2008) cannot be suspended in water because the direction of water pressure acting on the main body is vertically downwards.